Mr. Featherstonhaugh remarks, that the Natural Tunnel has not been
worn through the rock by the long-continued action of running water is
evident, not from the cavernous structure alone of the general country,
but from the form of Powell's mountain, in a spur of which the Tunnel
passes transversely.

Mr. Featherstonhaugh further concludes the Tunnel to be a natural cavity
in the rock, for, if such had not been the case, "it is evident that the
stream would have been deflected from its line; would have followed the
base of the hill, and have turned the extreme point."

Little is known of the geology of the country in which this Tunnel is
situate, notwithstanding the popularity of the natural bridges of the
State. The rock before us would appear to belong to that class which
geologists commonly term Perforated Mountains, which some suppose
to have been bored through, in part, at least, by the persevering
industry of man. "Such phenomena," observes Maltebrun, "are, however,
mere eccentricities of nature, and differ from caverns only from
the circumstance of having a passage entirely through them. The
Pierre-Pertuise in Mount Jura, and Pausilippo, near Naples, are
instances of this kind. The Torghat, in, Norway, is pierced by an
opening 150 feet high, and 3,000 long. At certain seasons of the year,
the sun can be seen darting its rays from one extremity to the other of
this vault. Near New Zealand is a rocky arch through which the waves of
the sea pass at high water."[4] The latter, one of the Piercy Islands,
will be found engraved and described in _The Mirror_, vol. xix. p. 145.


[1] See the Cut.